A. Field of the Invention
The present invention is in the field of animal health and relates to novel porcine parvovirus strains, including attenuated strains for vaccination, methods of manufacture and methods of treatment using vaccines obtained from said novel parvovirus strains.
B. Description of the Related Art
Parvoviruses infect a wide variety of animal species, and some of them are responsible for severe clinical diseases, but the majority of these viruses cause only mild or subclinical infections. They belong to the family Parvoviridae and form two subfamilies: Densovirinae, whose members infect insects, and Parvovirinae, whose members infect vertebrates. The latter subfamily currently includes five genera: Dependovirus, Erythrovirus, Amdovirus, Bocavirus and Parvovirus (1).
Parvovirus virions are non-enveloped and contain single-stranded, linear DNA genomes of approximately 5-6 kilobases (kb). The genome consists of two main open reading frames (ORF) that encode the non-structural and capsid proteins. The newly described bocaviruses carry a third ORF, between the two major ORFs (1).
The classical porcine parvovirus (PPV1) strains of the genus Parvovirus are widely distributed around the world and are responsible for reproductive disorders of pigs, especially in herds where vaccination protocols are not followed correctly or vaccine efficacy is decreased due to immunosuppressive factors. During the last decade, a number of new parvoviruses have been detected in pigs. These include porcine parvovirus 2 (PPV2) (2) and related viruses (3). A new group of porcine and bovine parvoviruses, namely the hokoviruses (PHoV, BHoV), were identified in Hong Kong (4), and these viruses were found to be genetically similar to human PARV4 and 5. Although they were originally named hokoviruses after Hong Kong, a new classification of PHoV as PPV3 was proposed (5). PPV4 shows the highest similarity to bovine parvovirus 2, but the coding capacity and genome organization are similar to those of bocaviruses, as PPV4 encodes an additional ORF3 like bocaviruses, located between ORF1 and ORF2. The PPV4-encoded putative ORF3 protein, however, is quite different from that of bocaviruses (5).
There is an ongoing need to monitor swine for the emergence of new viruses, and to develop vaccines, treatments and methods of detection for new viruses.